Method of firing tiles



Patented Dec. 10,1929 o J p 1,739,151

UNITED STATES PATENT OFFICE JONAS P. JOHNSON, OF SAN FRANCISCO, CALIFORNIA I METHOD OF FIRING TILES No Drawing. Application filed March 5, 1928. Serial No. 259,383.

This invention relates to the manufacture or cracking and produces a very evenly fired of clay products, especially clay tile such as body. floor and wall tile generally, and the object While I find the greatest value of my inof the invention is to provide a method of vention in connection with the firing of flat firing such tile in the kiln whereby the losses tiles, it is evident that it has value in the firdue to cracking and warping of the tiles is ing of any kind of clay bodies where the overcome. danger of warping and cracking is incurred.

In the common practice of firing or burn- I claim: ing tiles they are usually placed in saggers in The method of reducing the tendency of the kilns and the heat gradually raised over a clay tiles to warp and crack in firing which period of time extending to a couple of days, comprises arranging the tiles on edge in sagdepending on the size of the kiln, then maingers and spaced from each other, and resting tained atthe proper firing temperature for all along their lower edges on the bottom some hours, and the temperature lowered, thereof, filling the spaces between the tiles the fire extinguished, and after cooling sufiiand entirely covering the tiles with a granuciently the kiln is opened and the product relar material refractory to the firing heat,

moved. and of firing the tiles in a kiln While so cov- However, it is found that a large percentage ered. of the fired clay bodies are warped or cracked, JONAS P. JOHNSON.

and this is so even when the greatest of care has been used to avoid too rapid a change of temperature in heating and cooling.

Such loss being considered unavoidable simply had to be charged against general manufacturing expense, and some of the damaged product sold as seconds.

I have discovered a method of almost entirely overcoming the loss through warpage and cracking in the kiln which comprises completely covering the clay goods before firing with a powdered material able to withstand the firing heat, such for instance as any refractory sand, kieselguhr, or other powdered or granular material inert with relation to the clay bodies being fired.

Some clays of which tiles are made fire at a much lower temperature than others and consequently permit the use of sand which would fuse and stick to clays of higher firing temperatures.

In carrying out my process I preferably place the tiles on edge in saggers in the kiln in the usual way, but fill the saggers with sand of proper refractory nature so that the tiles are entirely covered, and preferably the spaces between the tiles, if standing on edge are also filled. When the kiln is filled 1 fire it in the usual manner.

The method described, results in substantially eliminating losses through warpage 

